The present invention relates to a cutting roller in a labeling machine with the continuous introduction of a reeled film of labels. In particular, the cutting roller finds its most extensive use to cut into segments or labels a thin film of polypropylene or PVC or plastic film in general whereon are printed the images and data constituting the label. It could nonetheless also be used for films made of other materials, for instance paper. Labeling machines that employ label films generally comprise:
an assembly for unwinding the reeled film;
a cutting assembly constituted by a vertical blade mounted on a roller rotating about a vertical axis, which in the technical jargon is called cutting roller, and by a fixed vertical counter-blade;
a drum for picking up and transferring the cut label towards a roller for spreading the glue which intervenes in predetermined areas of the label and subsequently on the container whereon the label itself is to be applied.
Both the cutting roller, bearing the blade, and the pick-up drum are provided internal chambers in which a vacuum is created and which communicate through a plurality of holes with the outer surface of the cutting roller or of the drum to attract and hold the labels while they are cut and transferred onto the drum and to retain them on the drum itself.
The cutting of the film, which in some cases has a thickness of a few hundredths of a millimeter, presents several problems due mainly to the flexion or deformation of the support of the cutting roller. Said flexion or deformation occurs mainly because of the inconsistent and inconstant heat expansions in the whole cutting roller. In particular, it is evident that at the start of the work process the supports of the cutting roller have low temperatures which progressively increase as the hours of work increase, so that one is forced to adjust the position of the counter-blade during the working period.
To overcome the aforesaid drawback, the same Applicant has provided a cutting roller (protected by Italian industrial invention Patent No. 1294078) which comprises ducts able to carry oil, heated at a temperature exceeding that of the external environment by about 20-30xc2x0 C., into the roller support frame. These ducts allow for heating said support frame to a temperature of about 50xc2x0 C. before starting the labeling cycle and for maintaining said temperature during the work of the machine.
The aim of the present invention is to eliminate the aforesaid drawbacks and to make available a cutting roller provided with a cooling system able to maintain constant the temperature of the supports of the cutting roller, exploiting compressed air at ambient temperature. A first advantage is thereby obtained of not having heating systems with the consequent lower operating costs. A second advantage consists of the lack of costly seal elements, with no leakage problems, since the cooling fluid is air.
Said aims are fully achieved by the cutting roller in a labeling machine with the continuous introduction of a reeled film of labels, constituting the subject of the present invention, which is characterized by the contents of the claims set out below.
In particular, the cutting roller comprises, in correspondence with the two supports of its rotation shaft, ducts wherein compressed air at ambient temperature is sent. In correspondence with said supports are provided temperature detection probes which activate or inhibit the flow of air by acting on appropriate solenoid valves inserted on the compressed air supply line.